Water discrimination fuze ball-bearing screw type



1961 H. n. SAUNDERSON 2,994,272

WATER DISCRIMINATION FUZE BALL-BEARING SCREW TYPE Filed March 25, 1956 5 Sheets-Sheet 1 FIG.

INVENTORQ H. D. SAUNDERSON flaw ATTORNEYS 1961 H. D. SAUNDERSON 2,994,272

WATER DISCRIMINATION FUZE BALL-BEARING SCREW TYPE Filed March 23, 1956 3 Sheets-Sheet 2 INVEN H. D. SAUNDER 9561 ATTOR N EY S Aug. 1, 1961 H. D. SAUNDERSON WATER DISCRIMINATION FUZE BALL-BEARING SCREW TYPE Filed March 23, 1956 DRAG DECELERATION (9) ENTRY DECELERATION (g) 5 Sheets-Sheet 3 ENTRY VELOCITY (feet per second) O 0.1 0.2 0.3 0.4 0.5 TIME AFTER ENTRY (seconds) FIG.5

FIG.6

INVENTOR. H. D. SAUNDERSON ATTOR NEYS FIG.4

Patented Aug. 1, 1961 2,994,272 WATER DISCRIMINATION FUZE BALL-BEARING SCREW TYPE Henry D. Saunderson, Riverside, Calif., assignor to the United States of America as represented by the Secretary of the Navy Filed Mar. 23, 1956, Ser. No. 573,575 6 Claims. (Cl. 102--70.2) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a fuze and more particularly to a water discrimination fuze of the ball bearing screw type which aligns a detonator and closes contacts within the fuze of a missile in response to the deceleration of the missile as it changes from a relatively high velocity in air to a much lower velocity in water.

Formerly direct mechanical means had been utilized to arm a missile which was either manually or automatically activated prior to or at the moment of release of the missile or alternatively the missile was armed by means of a timing device or a water flow meter after release. These devices were complex and subject to human failure and moreover were subject to mechanical failure.

A Water Discrimination Fuze of the multiple leaf type is disclosed in the co-pending application of H. D. Saunderson, filed MarchlS, 1956, Serial No. 571,851, now Patent No. 2,900,912, which overcomes many of the difliculties of the prior art devices but is somewhat complicated and is relatively inaccurate in integrating the deceleration of the missile containing the fuze.

Certain missiles have a normal course which consists of an air flight followed by entry into water and a subsequent run under the surface of the water. It is desirable to prepare the detonator within the fuze of such a missile so as to arm the missile after it has entered the water. It is also desirable that such a missile not be armed by the normal and accidental shock forces that are encountered in handling and shipping and that the fuze be simple, compact and completely enclosed or sealed in the missile.

One preferred embodiment of the present invention utilizes the inertia of a spring restrained mass having a ball bearing screw secured thereto to rotate a rotor in re-' sponse to the deceleration of the missile on water entry. After a predetermined movement of the rotor under continued deceleration over a period of time the rotor is retained by a detent in a position where the detonator is aligned with a hole in the rotor to provide explosive egress to the charge within the missile. Rotation of the rotor also actuates a cam which closes electrical contacts thereby preparing the detonator firing circuit for actuation by point detonation contacts on impact of the target.

One object of the present invention i to provide a simple fuze having a minimum of moving parts which will arm a missile having an initial air trajectory only after the missile enters the water and not before.

Another object of the present invention is to provide a water discrimination fuze which prepares a detonator by mechanical alignment and closing of electrical contacts for arming an air-water missile and where the preparation of the detonator depends on a predetermined and more precisely and continuously evaluated deceleration of the missile containing the fuze.

A still further object of the present invention is to provide means for arming a missile that contains an explosive charge and which has its trajectory consisting of a flight in air followed by entry into the water and a subsequent submerged run under water where in the missile is armed shortly after the missile enters the water and not before in response to a predetermined deceleration of the missile containing the fuze for a predetermined period of time.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal section of one preferred embodiment of the water discrimination fuze of the present invention;

FIG. 2 is a cross section of the fuze taken on the line 22 of FIG. 1;

FIG. 3 is a cross sectional view of the fuze taken on the line 33 of FIG. 1;

FIG. 4 is a schematic circuit diagram illustrating the electrical circuit for actuating the fuze of the present invention;

FIG. 5 is a graph illustrating the entry deceleration with regard to the velocity of a missile such as a specific torpedo as it leaves the air and enters the water; and

FIG. 6 is a graph illustrating the relation between time and deceleration of a missile such as a torpedo which has a specific entry velocity.

Referring now to the drawings in detail, FIG. 5 is a graph illustrating the entry decelerations for various entry velocities of a missile, such as a specific torpedo, as the trajectory changes from air to water. The ordinates are values of the entry deceleration measured in units of acceleration due to gravity g, where each unit g is approximately equal to 32.2 feet per second, while the abscissae are values of the missile velocity in feet per second at the moment the missile enters water. Assume that the entry velocity of a missile is 500 feet per second; then the corresponding entry deceleration of the missile is g.

FIG. 6 shows the deceleration characteristic due to water drag of a missile, such as a torpedo, that has an entry velocity of 500 feet per second. The ordinates are values of deceleration, measured in units of acceleration due to gravity g, caused by water drag acting on the missile while the abscissae represent values of time in seconds after the missile has entered water.

Assume that a missile, of the character indicated and which has a water entry velocity of 500 feet per second, moves for an interval of 0.1 second under water after the missile enters water; then the corresponding drag deceleration of the missile is 40 g. Moreover, if the missile moves for an interval of 0.2 second under Water after the missile enters water; then the drag deceleration of the missile decreases to 20 g. The area under the curve bounded by abscissae 0 and 0.1, and shown crosshatched, is a measure of the energy lost by a missile that has a water entry velocity of 500 feet per second during 0.1 second after the missile enters water. The area under the curve bounded by abscissae 0 and 0.2 second, comprising the sum of the crosshatched and lined areas, is a measure of the energy lost by the aforesaid missile during an interval of 0.2 second after the missile enters water. A mass, located withinthe missile and free to move or having little constraint in the direction of motion, is not subject to the same deceleration as that of the missile and i end of casing is provided with an annulus 14, to guide the lower portion of coil spring 15, and a hole 16 that contains a detonator 1 7. The lower portion of hole 16 has an enlargement 18 to receive detent 19 to be hereinafter described. A suitably proportioned piston" or inertia weight 22 'is positioned within the casing extension 13 and is constrained from rotational motion by pins 20- secured to casing extension 13 and provided with grooves 21 to permit motion in the direction of the arrow parallel to the longitudinal axis of the fuze. Cavity 23 in piston 22. provides a 'guidefor the upper portion of the slightly compressed coil spring 15. v

A ball-bearing screw '24'centrally located within casing 10 and casing extension 13 is secured to piston 22 by screw 25 and is positioned within rotor 26 which rotates as a ball-bearing nut on journal 27 within a bearing in partition 12 and'on' journal 28-within a bearing in the upper part of casing 10. Ball-bearing 29 provides for rotor 26 a nearly frictionless thrust bearing between journal 27 and the lower portion of the bearing in partition 12.

'A suitably located hole 30' in partition 12 provides explosive egress for detonator '17 to a booster adapted to be located in the space 31 and set off the charge within the missile, when rotor-"26 is rotated so that a stepped hole 32 therein is aligned with detonator 17 and hole 30. A thin-walled cylindrical tube 33,located within hole 32, is enlarged atthe upper end to form a detent 19 and is provided with a flange 34. A compressed coil spring 35 rests on the step inhole 32 and bears against flange 34 tohold detent 19 against the lower inner surface of casing 10. Ball-bearings 36 are suitably located and partial- 1y recessed in rotor 26 and engage with a spirally cut groove in ball-bearingscrew 24. A cam 37 is secured bya press fit on a slightly tapered extension of journal 28 and is positioned in a manner that contacts in pushbutton switch 38 are closed when the cam is rotated throughout 180 degrees, from the normal position of rotor 26 as illustrated in FIGS. 1 and2.

FIG. 4 shows the electrical circuit comprising detonating means 39 withinthe detonator, cam-operated pushbutton switch 38, auxiliary point detonation switch 40 which closes when the missile makes physical contact with the target, a source of electrical energy 41, and circuit return through the metallic frame of the missile, casing 10, and detonator 17 as indicated by ground connections 42.

Operation The operation of the fuze described above is as follows. The water discrimination fuze is mounted with the longitudinal axis of the same in line with or parallel to the longitudinal axis of the missile. At the outset, rotor 26 is positioned with push-button switch 38 open circuited and with tube 33 displaced 180 degrees from detonator 17 and explosive egress hole 30, being retained in this position by slightly compressed coil spring 15 that exerts a small force against piston 22 which is constrained from further movement by pins 20 in grooves 21 and which also positions ball-bearing screw 24. It will be noted that the water discrimination fuze of this invention is doubly safe in this position, since contacts of push-button switch 38 must be closed and the detonator 17, tube 33, and explosive egress hole 30 must be aligned mechanically before the explosive charge 31 can be ignited.

When a missile, having a fuze in the relative position indicated, changes fromfiight in air and enters water, a large entry deceleration of the missile takes place, as shown in FIG. 6. Since piston22 consists of a springrestrained but inertia responsive mass, the piston and at tached ball-bearing screw 24 move in the direction of the longitudinal axis of the fuze asindicated by the arrow and partially rotate rotor 26. If the decelerationof the missile continues due to water drag, piston 22' and at: tached ball-bearing screw 24 continue to move due, to eir in rti l en y. nt at a P e e ermined d ce1er nloifiher iss e. qtor. 6. w 11;.hav r0taf ed sq s,tq

align detonator 17, tube 33, and explosive egress hole 30. In this position spring 35 forces detent 19 into enlargement 18 to latch rotor 26 preventing same from returning to normal and cam 37 has rotated to operate push-button switch 38 to close contacts therein, thus preparing the fuze to arm the missile.

If the deceleration of the missile is other than in the longitudinal direction, that is, in the desired direction of travel of the missile, piston 22 and attached ballbearing screw 24 are subject only to the component of the inertial force acting in that direction and rotor 26 does not rotate or rotates only throughout a few degrees, after which, if the deceleration ceases, piston 22, ballbearing screw 24, and rotor 26 return to the normal position shown in FIGS. 3 and 4. Similarly if the deceleration that takes place in a longitudinal direction is less than the predetermined magnitude, or if the deceleration is of proper magnitude but does not persist beyond a critical time interval, inertial energy of piston 22 and attached ball-bearing screw 24 is insufficient to rotate rotor 26 throughout degrees and at the conclusion of the deceleration interval piston 22, ball-bearing screw 24, and rotor 26 return to their normal positions.

The construction of FIG. 1 embodies a cylindrical rotor that is subject to minimum damping. It will be understood thateddy-current, pneumatic, or hydraulic damping means or a combination of the same, may be incorporated in the rotor and casing to reduce rotational oscillations of the rotor.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A water discrimination fuze comprising a housing adapted to contain an explosive charge and be mounted within a missile having an air-water trajectory, aninertia weight slidably mounted in said housing for longitudinal movement parallel to the longitudinal axis of the missile, resilient means urging said weight in a direction opposite to the inertia forces due to deceleration of the missile on water entry, a rotor mounted for limited rotation about a longitudinal axis within said housing, a detonator mounted in a hole within said housing adjacent said rotor, an opening extending longitudinally through said rotor in an eccentric position and adapted to be moved into alignment with said detonator and the explosive charge, a tubular detent resiliently mounted in said opening and adapted to move into said hole to latch said rotor and provide explosive egress between said detonator and the explosive charge, screw means for translating the longitudinal movement of said inertia weight into rotational movement of said rotor, switch means associated with said detonator, and cam means on said rotor for actuating said switch in response to movement of said inertia weight.

2. A water discrimination fuze comprising a housing adapted to contain an explosive charge and be mounted within a missile having an air-water trajectory, said housing having two intermediate partitions, a detonator mounted eccentrically in one partition, a longitudinal opening aligned with said detonator in the other partition, a rotor mounted for rotation upon a longitudinal axis between said partitions, an inertia-weight mounted for longitudinal movement, resilient means urging said inertia-weight in one direction, a screw member attached to said inertiaweight and engaging said rotor whereby longitudinal movement of said inertia-weight is translated into rotational movement of said rotor, detent means in said rotor adapted to lock said rotor into position after a predetermined angular movement, and an opening in said rotor adapted to be moved into alignment with said detonatonand an opening through said partition.

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tent is mounted within said opening extending longitudinally through said rotor and comprises a cylindrical element providing explosive egress between said detonator and the opening through said other partition.

4. A water discrimination fuze comprising a housing adapted to contain an explosive charge and be mounted within a missile having an air-water trajectory, said housing having two intermediate partitions, a detonator mounted eccentnically in one partition, a longitudinal opening aligned with said detonator in the other partition, a rotor mounted for rotation upon a longitudinal axis between said partitions, an inertia-weight mounted for longitudinal movement, resilient means urging said inertia-weight in one direction, a screw member attached to said inertia-weight and engaging said rotor whereby longitudinal movement of said inertia-weight is translated into rotational movement of said rotor, detent means in said rotor adapted to lock said rotor in position after a predetermined angular movement, longitudinal opening in said rotor adapted to be moved into alignment with said detonator and the opening through said partition, a cam mounted on said rotor, and a switch connected to said detonator and positioned for actuation by said cam upon rotation of said rotor.

5. A fuze as set forth in claim 4 wherein said detent is mounted within said opening extending longitudinally through said rotor and comprises a cylindrical element providing explosive egress between said detonator and the opening through said other partition.

6.- A water discrimination fuze comprising a housing adapted to contain an explosive charge and be mounted within a missile having an air-water trajectory, said housing having two intermediate partitions, a detonator mounted eccentrically in one partition, a longitudinal opening aligned with said detonator in the other partition, a rotor mounted for rotation upon a longitudinal axis between said partitions in said housing, an inertia-weight mounted for longitudinal movement, resilient means urging said inertia-weight in one direction, a ball-bearing screw member attached to said inertia-Weight and engaging said rotor whereby longitudinal movement of said inertia-weight is translated into a rotational movement of said rotor, detent means in said rotor adapted to lock said rotor into position after a predetermined angular movement, an opening in said rotor adapted to be moved into alignment with said detonator and the opening through said partition, a cam mounted on said rotor, and a switch connected to said detonator and positioned for actuation by said cam upon rotation of said rotor.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,120 Semi Apr. 26, 1949 2,666,390 Brandt Jan. 19, 1954 

